This invention relates to novel aromatic poly(ether ketones) having imide, amide, ester, azo, quinoxaline, benzimidazole, benzoxazole, or benzothiazole groups and to methods for their preparation, particularly to electrophilic polymerization in the presence of a Lewis acid and a complex between a Lewis acid component and a Lewis base component and, optionally, a diluent.
Aromatic poly(ether ketones), in particular those wherein the aromatic groups are all para-linked, possess many desirable properties, for example, high temperature stability, mechanical strength, and resistance towards common solvents. Unlike many other "high temperature stable" polymers, they are melt processable on conventional euqipment.
It has now been discovered that the incorporation of imide, amide, ester, azo, quinoxaline, benzimidazole, benzoxazole, or benzothiazole groups into an aromatic poly(ether ketone) results in a polymer having surprisingly superior properties over known aromatic poly(ether ketones). Further, the resulting polymer has unexpectedly superior properties or processability compared to aromatic polymers having imide, amide, ester, azo, quinoxaline, benzimidazole, benzoxazole, or benzothiazole groups. Methods for preparing aromatic poly(ether ketones) having functional groups such as amide, ester, imide, azo, benzimidazole, benzothiazole, benzoxazole, quinoxaline, and the like have also been discovered.
Aromatic poly(ether ketones) can be prepared by Friedel Crafts synthesis in which an aryl ketone linkage is formed from a carboxylic acid halide and an aromatic compound having an activated hydrogen, i.e., a hydrogen atom displaceable under the electrophilic reaction conditions. The monomer system employed in the reaction can be, for example, (a) a single aromatic compound containing a carboxylic acid halide as well as an aromatic carbon bearing a hydrogen activated towards electrophilic substitution; or (b) a two-monomer system of a dicarboxylic acid dihalide and an aromatic compound containing two such activated hydrogens.
A common medium for such Friedel Crafts reactions consists of the reactant(s), a catalyst, such as anhydrous aluminum chloride, and an inert solvent such as methylene chloride. Because carbonyl groups complex with aluminum trichloride and thereby deactivate it, the aluminum chloride catalyst is generally employed in the preparation of arylene ketones in an amount slightly more than one equivalent for each equivalent of carbonyl groups in the reaction medium. The slight excess assures that enough free aluminum chloride will be present to fulfill its catalytic role. Other metal halides such as ferric chloride may be employed as the catalyst, but generally with less satisfactory results.